In case you were wondering. LEGO Cuusoo is an official LEGO design incubator. Members can post an idea for a set. If at least 10,000 other members support the idea, then LEGO evaluates the idea against a set of metrics (playability, cost, branding, etc). If it passes that final evaluation, then LEGO will start selling the set as part of their official line.
(The person or group that made the initial submission then get a 1% royalty of net sales)
The two biggest factors in LEGO set price are licensing costs and piece count. That's why official sets tend to be simpler than fan sets. When they do make complicated and large builds, they tend to be expensive, like $100 for the Sopwith Camel.
CUUSOO is part of LEGO. After a CUUSOO project reaches 10k supporters, it goes through a review by LEGO corporate which includes stuff like Brand Fit Analysis (too violent?) and Business Case Development (will this actually sell?) and License Agreements (can we license this?). If it passes that, then it gets a model designed by a LEGO designer which is not necessarily the same as the submitted idea.
That is not quite right. Cuusoo is a Japanese company and independent from Lego. (In the beginning Lego Cuusoo also launched only in Japan – but it blew up internationally.) They offer their “social creation platform” (also called Cuusoo) to customers – of which Lego is now most certainly their biggest and most prominent one. I’m unsure of the exact relationship, but I think it’s fair to say that Cuusoo is a SaaS business.
Cuusoo seems to host the platform and I assume (but don’t know) that they take care of all technical issues, Lego seems to take care of the review process. So Lego Cuusoo is basically the Cuusoo installation run by Lego.
You are completely correct about the review process, though (basically everything you wrote after the first sentence).